The present invention relates to a gallium nitride group semiconductor and a light emitting diode comprising it and the process of producing the same.
In the past, the semiconductor and the light emitting diode formed by the vapor growth of a thin film of gallium nitride group semiconductor (Al.sub.x Ga.sub.1-x N; inclusive of x=0) on a sapphire substrate using the process of metalorganic vapor phase epitaxy (hereinafter referred to as "MOVPE") have been studied.
The MOVPE forming the light emitting diode and the semiconductor is conducted by using a vapor growth apparatus as shown in FIG. 10. In the vapor growth apparatus, a manifold 6 is connected to a quartz reaction tube 7 and a supply system A of NH.sub.3, a supply system B of H.sub.2 and N.sub.2, a supply system C of trimethylgallium (hereinafter referred to as "TMG") of an organometallic compound gas, a supply system D of trimethylaluminum (hereinafter referred to as "TMA") of the organmetallic compound gas and a supply system E of diethylzinc (hereinafter referred to as "DEZ") which is a reactant gas containing a doping element (hereinafter referred to as "dopant gas") are connected to the manifold 6. Also, in the quartz reaction tube 7, a high frequency heating graphite susceptor 9 is provided, on which a sapphire substrate 10 is disposed, which is heated by a high frequency coil 8. Each reactant gas and carrier gas from each supply system are mixed in the manifold 6, and the mixed gas is led to the quartz reaction tube 7 and blown against the sapphire substrate 10 to grow an Al.sub.x Ga.sub.1-x N thin film thereon.
Then, by changing the mixing ratio of each organometallic compound gas, the composition ratio can be changed and the insulated thin film of I-type (Intrinsic) Al.sub.x Ga.sub.1-x N can be formed by doping zinc.
Also, one example of the light emitting diode produced specifically by the aforementioned MOVPE is, as shown in FIG. 9, constructed as such that an N layer 12 consisting of N-type GaN and an I layer 13 consisting of I-type GaN formed by doping zinc are formed on the sapphire substrate 10, an electrode 15 is formed on the upper surface of the I layer 13 and an electrode 16 is formed on the side of the N layer 12 so that the both layers are luminous at their joint.
Since the sapphire substrate is utilized in the light emitting diode, the electrode 16 has to be positioned on the side of the N layer 12, encountering difficulty in production.
Meanwhile, when forming the electrode 16 of the N layer 12 on the same surface as the electrode 15 of the I layer 13, it has been attempted to form the electrode on the N layer exposed by removing an insulated film, after selectively forming the I layer by masking with the insulated film evaporated in a prescribed pattern.
However, since selective growth of the I layer with the insulated film mask is somewhat difficult and the I layer is formed also on the insulated film, making removal of the insulated film alone is difficult.
In the past, when the vapor growth of the gallium nitride group semiconductor takes place on the sapphire substrate, a surface c ({0001}) has been considered appropriate as the main surface which is involved in the crystal growth.